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pve-qemu/debian/patches/pve/0051-PVE-Backup-Use-a-trans...

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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Stefan Reiter <s.reiter@proxmox.com>
Date: Thu, 20 Aug 2020 14:25:00 +0200
Subject: [PATCH] PVE-Backup: Use a transaction to synchronize job states
By using a JobTxn, we can sync dirty bitmaps only when *all* jobs were
successful - meaning we don't need to remove them when the backup fails,
since QEMU's BITMAP_SYNC_MODE_ON_SUCCESS will now handle that for us.
To keep the rate-limiting and IO impact from before, we use a sequential
transaction, so drives will still be backed up one after the other.
Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
---
pve-backup.c | 167 +++++++++++++++------------------------------------
1 file changed, 49 insertions(+), 118 deletions(-)
diff --git a/pve-backup.c b/pve-backup.c
index 1e7b92a950..f3df43eb8c 100644
--- a/pve-backup.c
+++ b/pve-backup.c
@@ -52,6 +52,7 @@ static struct PVEBackupState {
VmaWriter *vmaw;
ProxmoxBackupHandle *pbs;
GList *di_list;
+ JobTxn *txn;
QemuMutex backup_mutex;
CoMutex dump_callback_mutex;
} backup_state;
@@ -71,32 +72,12 @@ typedef struct PVEBackupDevInfo {
size_t size;
uint64_t block_size;
uint8_t dev_id;
- bool completed;
char targetfile[PATH_MAX];
BdrvDirtyBitmap *bitmap;
BlockDriverState *target;
+ BlockJob *job;
} PVEBackupDevInfo;
-static void pvebackup_run_next_job(void);
-
-static BlockJob *
-lookup_active_block_job(PVEBackupDevInfo *di)
-{
- if (!di->completed && di->bs) {
- for (BlockJob *job = block_job_next(NULL); job; job = block_job_next(job)) {
- if (job->job.driver->job_type != JOB_TYPE_BACKUP) {
- continue;
- }
-
- BackupBlockJob *bjob = container_of(job, BackupBlockJob, common);
- if (bjob && bjob->source_bs == di->bs) {
- return job;
- }
- }
- }
- return NULL;
-}
-
static void pvebackup_propagate_error(Error *err)
{
qemu_mutex_lock(&backup_state.stat.lock);
@@ -272,18 +253,6 @@ static void coroutine_fn pvebackup_co_cleanup(void *unused)
if (local_err != NULL) {
pvebackup_propagate_error(local_err);
}
- } else {
- // on error or cancel we cannot ensure synchronization of dirty
- // bitmaps with backup server, so remove all and do full backup next
- GList *l = backup_state.di_list;
- while (l) {
- PVEBackupDevInfo *di = (PVEBackupDevInfo *)l->data;
- l = g_list_next(l);
-
- if (di->bitmap) {
- bdrv_release_dirty_bitmap(di->bitmap);
- }
- }
}
proxmox_backup_disconnect(backup_state.pbs);
@@ -322,8 +291,6 @@ static void pvebackup_complete_cb(void *opaque, int ret)
qemu_mutex_lock(&backup_state.backup_mutex);
- di->completed = true;
-
if (ret < 0) {
Error *local_err = NULL;
error_setg(&local_err, "job failed with err %d - %s", ret, strerror(-ret));
@@ -336,20 +303,17 @@ static void pvebackup_complete_cb(void *opaque, int ret)
block_on_coroutine_fn(pvebackup_complete_stream, di);
- // remove self from job queue
+ // remove self from job list
backup_state.di_list = g_list_remove(backup_state.di_list, di);
- if (di->bitmap && ret < 0) {
- // on error or cancel we cannot ensure synchronization of dirty
- // bitmaps with backup server, so remove all and do full backup next
- bdrv_release_dirty_bitmap(di->bitmap);
- }
-
g_free(di);
- qemu_mutex_unlock(&backup_state.backup_mutex);
+ /* call cleanup if we're the last job */
+ if (!g_list_first(backup_state.di_list)) {
+ block_on_coroutine_fn(pvebackup_co_cleanup, NULL);
+ }
- pvebackup_run_next_job();
+ qemu_mutex_unlock(&backup_state.backup_mutex);
}
static void pvebackup_cancel(void)
@@ -371,36 +335,28 @@ static void pvebackup_cancel(void)
proxmox_backup_abort(backup_state.pbs, "backup canceled");
}
- qemu_mutex_unlock(&backup_state.backup_mutex);
-
- for(;;) {
-
- BlockJob *next_job = NULL;
-
- qemu_mutex_lock(&backup_state.backup_mutex);
-
- GList *l = backup_state.di_list;
- while (l) {
- PVEBackupDevInfo *di = (PVEBackupDevInfo *)l->data;
- l = g_list_next(l);
+ /* it's enough to cancel one job in the transaction, the rest will follow
+ * automatically */
+ GList *bdi = g_list_first(backup_state.di_list);
+ BlockJob *cancel_job = bdi && bdi->data ?
+ ((PVEBackupDevInfo *)bdi->data)->job :
+ NULL;
- BlockJob *job = lookup_active_block_job(di);
- if (job != NULL) {
- next_job = job;
- break;
- }
- }
+ /* ref the job before releasing the mutex, just to be safe */
+ if (cancel_job) {
+ job_ref(&cancel_job->job);
+ }
- qemu_mutex_unlock(&backup_state.backup_mutex);
+ /* job_cancel_sync may enter the job, so we need to release the
+ * backup_mutex to avoid deadlock */
+ qemu_mutex_unlock(&backup_state.backup_mutex);
- if (next_job) {
- AioContext *aio_context = next_job->job.aio_context;
- aio_context_acquire(aio_context);
- job_cancel_sync(&next_job->job);
- aio_context_release(aio_context);
- } else {
- break;
- }
+ if (cancel_job) {
+ AioContext *aio_context = cancel_job->job.aio_context;
+ aio_context_acquire(aio_context);
+ job_cancel_sync(&cancel_job->job);
+ job_unref(&cancel_job->job);
+ aio_context_release(aio_context);
}
}
@@ -459,51 +415,19 @@ static int coroutine_fn pvebackup_co_add_config(
goto out;
}
-bool job_should_pause(Job *job);
-
-static void pvebackup_run_next_job(void)
-{
- assert(!qemu_in_coroutine());
-
- qemu_mutex_lock(&backup_state.backup_mutex);
-
- GList *l = backup_state.di_list;
- while (l) {
- PVEBackupDevInfo *di = (PVEBackupDevInfo *)l->data;
- l = g_list_next(l);
-
- BlockJob *job = lookup_active_block_job(di);
-
- if (job) {
- qemu_mutex_unlock(&backup_state.backup_mutex);
-
- AioContext *aio_context = job->job.aio_context;
- aio_context_acquire(aio_context);
-
- if (job_should_pause(&job->job)) {
- bool error_or_canceled = pvebackup_error_or_canceled();
- if (error_or_canceled) {
- job_cancel_sync(&job->job);
- } else {
- job_resume(&job->job);
- }
- }
- aio_context_release(aio_context);
- return;
- }
- }
-
- block_on_coroutine_fn(pvebackup_co_cleanup, NULL); // no more jobs, run cleanup
-
- qemu_mutex_unlock(&backup_state.backup_mutex);
-}
-
static bool create_backup_jobs(void) {
assert(!qemu_in_coroutine());
Error *local_err = NULL;
+ /* create job transaction to synchronize bitmap commit and cancel all
+ * jobs in case one errors */
+ if (backup_state.txn) {
+ job_txn_unref(backup_state.txn);
+ }
+ backup_state.txn = job_txn_new_seq();
+
/* create and start all jobs (paused state) */
GList *l = backup_state.di_list;
while (l) {
@@ -524,7 +448,7 @@ static bool create_backup_jobs(void) {
BlockJob *job = backup_job_create(
NULL, di->bs, di->target, backup_state.speed, sync_mode, di->bitmap,
bitmap_mode, false, NULL, BLOCKDEV_ON_ERROR_REPORT, BLOCKDEV_ON_ERROR_REPORT,
- JOB_DEFAULT, pvebackup_complete_cb, di, 1, NULL, &local_err);
+ JOB_DEFAULT, pvebackup_complete_cb, di, backup_state.txn, &local_err);
aio_context_release(aio_context);
@@ -536,7 +460,8 @@ static bool create_backup_jobs(void) {
pvebackup_propagate_error(create_job_err);
break;
}
- job_start(&job->job);
+
+ di->job = job;
bdrv_unref(di->target);
di->target = NULL;
@@ -554,6 +479,10 @@ static bool create_backup_jobs(void) {
bdrv_unref(di->target);
di->target = NULL;
}
+
+ if (di->job) {
+ job_unref(&di->job->job);
+ }
}
}
@@ -944,10 +873,6 @@ err:
PVEBackupDevInfo *di = (PVEBackupDevInfo *)l->data;
l = g_list_next(l);
- if (di->bitmap) {
- bdrv_release_dirty_bitmap(di->bitmap);
- }
-
if (di->target) {
bdrv_unref(di->target);
}
@@ -1036,9 +961,15 @@ UuidInfo *qmp_backup(
block_on_coroutine_fn(pvebackup_co_prepare, &task);
if (*errp == NULL) {
- create_backup_jobs();
+ bool errors = create_backup_jobs();
qemu_mutex_unlock(&backup_state.backup_mutex);
- pvebackup_run_next_job();
+
+ if (!errors) {
+ /* start the first job in the transaction
+ * note: this might directly enter the job, so we need to do this
+ * after unlocking the backup_mutex */
+ job_txn_start_seq(backup_state.txn);
+ }
} else {
qemu_mutex_unlock(&backup_state.backup_mutex);
}
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